Most modern hardwood floors, with the exception of a few, are finished with a layer of polyurethane. Polyurethane is a polymer that is suspended in a solvent. It is applied to the floor, and the solvent evaporates, leaving behind only the polymer. Essentially, it is a can of liquid plastic that is applied over your flooring. There are two basic kinds of polyurethane, oil-based and water-based. Each one is going to act differently immediately and over time. Here’s what will happen.
When you apply polyurethane to your stained floor, it will have a few immediate effects. Water-based polyurethane goes on fairly clear. It is also low odor. You’ll need to wait several hours before you can touch the polyurethane and even longer before you can walk on it. However, the most common visual effect is a deepening of the colors and the grain on the wood. If you choose a glossy polyurethane, it will shimmer and almost look wet. A matte water-based polyurethane is basically invisible once it’s dry.
An oil-based polyurethane is a little more dramatic. Most oil-based polyurethanes have a very slight amber hue. When you apply the polyurethane, you’ll notice that the floor becomes slightly tinted amber. That’s a very good way to deepen and enrich the colors of the floor.
There are long-term effects to the polyurethane choices as well. Water-based polyurethane typically doesn’t last quite as long as oil-based polyurethane before it needs to be repaired. However, it maintains the same quality throughout the time that it is applied as long as you don’t let it get so scratched up that it becomes cloudy.
Oil-based polyurethane, on the other hand, will start to turn a deeper shade of amber. This yellowing is desirable for some people. It creates warmer colors on your floor and makes it seem a little more rustic. Others don’t like the yellowing.
There are also concerns about volatile organic compounds (VOCs). These are chemicals that can vaporize at room temperature. The off-gassing can result in pollution or even health effects. Most polyurethanes are designed to have minimal VOCs. Oil-based polyurethanes sometimes have more VOCs than water-based, though. Over time, that could be a factor.
These are a few things to consider and to expect when applying polyurethane to your floor. You’ll need to reapply it every few years. Most flooring experts will say that a polyurethane coat lasts about 15 years.